Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 161436
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
936 AM EST Sat Dec 16 2017

.SYNOPSIS...
Lake effect snows will continue across portions of the forecast area
today before high pressure brings an end to the snowfall by this
evening. This high will cross the region tonight and Sunday, with
dry weather for the second half of the weekend. Temperatures will
warm above freezing Monday as a warm front lifts across the region,
bringing a chance for rain and snow showers into Tuesday before a
cold front sweeps across the lower Great Lakes Tuesday night,
bringing a return to more wintry conditions by Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Regional radars showing the Lake Ontario snow band pushing south
as a potent shortwave drops across the lake. This will bring a
short period of snow to areas south of the lake, including the
Rochester metro through early this afternoon, though amounts
should be modest as flow will be increasingly sheared and
moisture diminishing.

Enhanced lake snows will persist through the afternoon hours
east of Lake Erie. Highest snowfall totals will be across the
Chautauqua Ridge. By the end of the day, we should see snow wind
down even there, as flow veers to the northeast and high
pressure begins to build into the region. The passage of the
shortwave and the approach of the warm frontal boundary mean
that the coldest air will be past our region today, and
temperatures should rise into the mid to upper 20s across most
areas.

The aforementioned area of high pressure will moves across the lower
Great Lakes tonight, allowing for clearing skies, at least across
the northern zones. The nearby warm front will likely keep clouds in
place from the Thruway corridor south overnight. This will produce a
sharp temperature gradient across the forecast area, with lows
ranging from around 20 near the PA border to the single digits below
zero in the North Country.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
Expect a short warm up early next week after experiencing more than
10 days with below normal temperatures. High pressure passing from
NY into New England on Sunday will provide dry weather for most of
the day with increasing clouds ahead of an approaching warm front.
The warm front will be associated with a weak surface low tracking
across the Great Lakes. Temps should average below normal to close
out the weekend before the warm front arrives Sunday night. Highs
will range from the mid to low 30s in WNY and upper teens to mid 20s
for the North Country. Sunday night, we have continued chance POPs
for snow showers arriving ahead of the warm front which could mix
with some rain in the Niagara Frontier late. Forcing is not quite
strong enough to warrant anything higher than chance POPs at this
time.

We will then see above normal temps Monday and Tuesday behind the
warm front and within fairly zonal flow at 500mb. 850mb temps
rebounding back closer to 0C into Tuesday should translate into
surface highs in the mid 30s-40 Monday and upper 30s to mid 40s
Tuesday. A leading shallow shortwave trough passing over the Great
Lakes on Monday will then be followed by a broad but deepening
trough on Tuesday and Tuesday night. Each of these will be
accompanied by modified Pacific moisture resulting in continued
chance POPs for daytime rain showers and nighttime rain/snow
showers. The exception seems to be for the eastern Lake Ontario
region where models indicate better forcing and moisture will
combine for likely POPs. Later Tuesday into Tuesday night, a cold
front is forecast to cross our region supported by the mid level
trough. These features will drive higher POPs for rain showers
especially east of the lakes which will mix with or change to lake
enhanced and upslope driven snow showers overnight as cold air
deepens and overnight temps dip back into the 20s overnight. No
significant weather hazards are expected.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
High POPs for lake effect snows remain in place Wednesday as
northwest cold air advection drops 850mb temps to around -12C. This
flow would mainly impact locations southeast of the lakes. Outside
of the lake effect, chance POPs remain in between the lake effect
areas to cover for stray snow showers in weaker lake streamers south
of the lakes. Have lingered chance POPs for snow showers south of
the lakes into Wednesday night but expect some winding down as
surface-based ridging and drier air build into the region.
Temperatures will have returned to a little below average with highs
mainly in the upper 20s to lower 30s on Wednesday followed by lows
ranging from the teens to lower 20s Wednesday night.

Mainly dry weather expected Thursday with temps returning to near
normal before models show a stronger low pressure system crossing
the Great Lakes into New England Thursday night into Friday.
Southerly flow ahead this system should bring back above normal
temps for Friday along with increased precipitation probabilities.
Likely POPs have been forecast by Friday with an initial ptype of
snow gradually giving way to more in the way of rain over time as
temperatures warm.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
Lake effect snows will continue to affect areas downwind of Lake
Erie and Ontario into this afternoon. Northwesterly flow will keep
bands south of KBUF/KIAG/KART, however KJHW will continue to see
MVFR/IFR conditions through 18Z. The passage of a final upper level
disturbance will shove the Lake Ontario band south of the lake
around 18Z, bringing a brief period of -SHSN and potential MVFR/IFR
conditions to KROC. Otherwise, outside of lake bands, expect
VFR/MVFR conditions to persist through the TAF period.

Outlook...

Sunday...VFR.
Sunday night...MVFR with a chance of snow showers.
Monday...IFR/MVFR with a chance for rain and snow showers.
Tuesday...IFR/MVFR with rain likely.
Wednesday...IFR in lake effect snow likely SE of the Lakes,
MVFR/VFR in chance of snow elsewhere.
Thursday...Mainly VFR.

&&

.MARINE...
Small craft advisories remain in effect into this afternoon for most
zones, as a cold westerly wind continues to stir the waters of the
lakes. Winds will veer to the north, and eventually the northeast as
an upper level disturbance cross the region. This will be followed
rapidly by high pressure, which will bring winds down tonight, and
allow for calmer conditions on the lakes for the second half of the
weekend.

Southwest winds will begin to freshen on Monday, as a warm front
lifts across the lower Great Lakes and a trough of low pressure
associated with a deep low pressure system over James Bay
approaches the region. This will likely necessitate a round of small
craft advisories for Lake Erie by Monday night, and eastern Lake
Ontario by Tuesday morning.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Lake Effect Snow Warning until 1 PM EST this afternoon for
     NYZ006-008.
     Lake Effect Snow Warning until 4 PM EST this afternoon for
     NYZ019-020.
     Winter Weather Advisory until 1 PM EST this afternoon for
     NYZ012-085.
     Winter Weather Advisory until 4 PM EST this afternoon for
     NYZ021.
MARINE...Small Craft Advisory until 1 PM EST this afternoon for LEZ040-
         041.
         Small Craft Advisory until 7 PM EST this evening for
         LOZ042>045.

&&

$$

SYNOPSIS...TMA/WOOD
NEAR TERM...TMA/WOOD
SHORT TERM...SMITH
LONG TERM...JJR/SMITH
AVIATION...TMA/WOOD
MARINE...TMA/WOOD



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